Secondary electron multiplier



March 14, 1939. M LOKE A 2,150,632

SECONDARY ELECTRON MULTIPLIER Filed July 6, 1937 yaw a ia B0 10 ljoo y- U l m lll'i'i INVENTOR-S- ATTORNEY.

Patented Mar. 14, 1939 UNITED STATES PATENT OFFICE SECONDARY ELECTRON MULTIPLIER Application July 6, 1937, Serial No. 152,279 In Germany July 4, 1936 3 Claims.

(Granted under the provisions of sec. 14, act of March 2, 1927; 357 0. G. 5)

The invention relates to improvements in secondary electron multipliers adapted particularly for sound film reproduction and also for television purposes.

5 Hereto-fore it was customary to provide secondary electron multipliers operating according to the electrostatic principle with a plurality of spaced electrodes, each provided with a suitable layer so as to emit progressively multiplied sec.-

10 ondary electrons when. struck by the electron beam tobe: amplified. Similarly, the companion electrodes arranged opposite said first mentioned emitting electrodes and which were positioned to accelerate the released secondary elecl5 trons, heretofore consisted of a plurality of spaced individual electrodes. Obviously, the employment of a relative great number of. electrodes makes the construction of the secondary electron multiplier very complicated.

20 It is now an object of the present invention to simplify the construction of the secondary electron multiplier by combining all the spaced photosensitive electrodes to a Single photosensitive electrode.

; Another object of the invention is to combine all the previously used spaced accelerating electrodes to a. single accelerating electrode.

In particular, the invention has as its object a secondary electron multiplier in which a plum rality of photosensitive layers, is arranged upon a single carrier, the electron beam being successively conducted to these layers to be amplified by multiplication of the emitted secondary electrons.

; The invention also has the object of providing a secondary electron multiplier in which a single accelerating electrode is used, and in which a'ccelerating fields are arranged between the multiple photosensitive electrode and the accelerating electrode, which accelerating fields are produced by a drop of potential lengthwise of said electrodes.

The drawing illustrates by way of example a few embodiments of the new secondary electron multiplier.

In the drawing:

Fig. 1 is a diagrammatic view of one embodiment of the secondary electron multiplier of the present invention, and

) Fig. 2 illustrates in. plan view the grid structure employed in the secondary electron multiplier.

The secondary electron multiplier of the invention preferably is provided with a hermeti- 5 cally-sealed envelope I of ceramic material.

Within the envelope l are mounted two parallel plate-like plane electrodes 2 and 3, which are spaced from each other and extend in longitu-- dinal direction of the envelope l. The electrodes 2 and 3 consist of a semi-conductor as carbon, 5 slate or the like,,which serves as a carrier for a photo-electric layer 4 which emits secondary electrons when struck by an electron beam. Such a layer may consist of. a caesium-silver oxide coating.

A grid, which serves as accelerating electrode, is arranged between the two plate-like electrodes 2 and 3. The grid may consist of two semiconductor rods 5 (Fig. 2) which are mounted parallel to the plate electrodes and then are connected with each other by metallic conductors, for instance by a wire 6. The rods 5 are kept spaced from each other by suitable insulating bars 8.

At one end of the envelope l is mounted the collector or output electrode 1 and in front of the same is arranged a protecting grid Ill. The wall of the envelope I is provided with a transparent Window 9 constructed as photocathode.

The ends of the plate-like electrodes 2, 3 and of the accelerating grid 5, 6 are connected, as shown in; Fig. 1, with a source of potential the positive value of which increases lengthwise of the electrodes in a direction toward the collector or output electrode 1. Under the influence of the accelerating field and a. magnetic field the electrons are guided along the plate electrodes 2 and 3 in a curved path so as to strike the plate electrodes repeatedly at successive points, the potentials of which are higher than that of each 5 preceding point. This has the result that the electrons are multiplied until the final electron current is collected by the output electrode 1.

It is likewise within the scope of the present invention to employ as secondary electron emitting layer a material as it has already been provided in a prior application (Gorlich, Serial No. 94,589, filed August 6, 1936) for Photocathodes. According to this prior application a coating of caesium or rubidium is deposited by vaporization upon a coating of antimony or bismuth, whereupon the combined coatings are subjected to a special treatment, for instance a heat treatment, so that both metal coatings are alloyed.

It is believed obvious that various other modifications may be made without departing from the spirit and scope of the present invention.

What we claim is:

1.. A secondary electron multiplier comprising an envelope provided with a transparent photocathode and containing two spaced plate-like electrodes provided with a layer adapted to emit secondary electrons when struck by an electron beam, a grid between said electrodes and adapted to act as accelerating electrode, and a collecting electrode, and means adapted to connect difierent points of said two plate-like electrodes and said grid electrode with different potentials.

2. A secondary electron multiplier comprising an envelope provided witha transparent photocathode and containing two spaced plate-like electrodes provided with a layer adapted to emit secondary electrons when struck by an electron beam, a grid between said electrodes and adapted to act as accelerating electrode, and a collecting electrode, and means adapted to connect difierent points of said two plate-like electrodes and said grid electrode with different potentials, said grid electrode comprising two spaced rodlike members of semi-conductive material and metallic wires conductively connecting said two rod-like members with one another.

3.A secondary electron multiplier comprising an envelope provided with a transparent photocathode and containing two spaced plate-like electrodes provided with a layer adapted to emit secondary electrons when struck by an electron beam, 2, grid between said electrodes and adapted to act as accelerating electrode, a collecting electrode, and means adapted to connect different points of said two plate-like electrodes and said grid electrode with different potentials, said secondary electron emitting layer on said electrodes being each composed of two coatings, one coating consisting of an element of the group which comprises antimony and bismuth and the other coating consisting of an element of the group which comprises caesium and rubidium, both coatings being alloyed together.

MARTIN PLOKE. WILHELM LANG. 

